Looking at its distributed nature and syndication, David Weinberger calls it a networked book. futureofthebook has been wondering about this for a while, although Pulse is, so far, a more traditionally single-authored work. It links out frequently, non unlike the model Web 1.0, but with an eye towards social connections.
Put another way, it's also an experiment in publishing with social microcontent. Pulse appears in small pieces, each equipped with Technorati tags, user ratings, comments, and links for del.icio.us and digg. The whole work has a tag cloud, tweaked for most viewed tags and recently viewed ones. You can read it via email or RSS. Online, the core text, which will appear on printed pages, is now combined with a social computing layer, inlcuding content generated in multiple ways by many people beyond the author.
The whole thing starts with this post.
EDITED TO ADD: the creative team wrote up a nice account of the project as Web 2.0 effort.